1. Field of the Invention
The present invention relates to the field of pumps and pump attachments.
2. Prior Art
Piston and diaphram pumps are well known in the art and have been used to pump a wide variety of materials. Such pumps usually utilize a ball valve comprised of a ball and valve seat disposed to the pump in order to achieve unidirectional flow and a means for drawing the piston or diaphram. A preferred embodiment is a dual piston pump adapted to pump concrete. Hereinafter the present invention will be described with reference to such pumps. It is to be understood, that single and multiple piston pumps are within the scope of the present invention and give advantageous results when used in accordance with the present invention hereinafter described. Further materials other than concrete may advantageously be pumped by the pump manifold assemblies within the scope of the present invention. floors or walls are being constucted in a multi floored dwelling, the concrete can be mixed on the ground or in transit in readimix trucks and then pumped to the desired elevation for use. However, these prior art pumps have a number of shortcomings which, until the present invention, tended to cause surge in the concrete pressure and flow, causing accelerated wear and deterioration of the pump and associated equipment.
The source of the surge may be appreciated by considering the nature of the task such pumps are required to perform. Typically such pumps utilize ball valves, with one valve controlling the unidirectional flow for providing an inlet to a piston clinder assembly, and a second valve for providing a unidirectional flow outlet for that piston cylinder assembly. The ball valves are characterized by a valve seat of a smaller diameter than the ball, with the ball motion being theoretically limited in travel between the ball seat and some limiting or stopping device such as a pin or other device for retaining the ball within bounds. Pumps characteristically utilize a dual piston cylinder arrangement whereby one piston delivers concrete to the outlet port during one half of the delivery cycle, with the second piston havng a specially shaped stroke intended to maintain uniform flow through the first half of the cycle and to itself deliver concrete during the second half of the cycle to similarly maintain the flow during the intake stroke of the first piston. While theoretically uniform delivery pressure and flow from the dual piston pump is not too difficult to obtain, secondary effects have a substantial effect on the ball valve performance which in turn can cause excessive surging in the flow and pressure of the concrete delivered by the system. In particular, the balls in the ball valves in practice do not actually totally close against the valve seat, but instead tend to close within approximately the aggregate size of the valve seat. Accordingly, as aggregate size varies from pea gravel to aggregate up to as large as three-fourths inch, the so-called closed position of the balls in the ball valves may vary by a substantial part of an inch.. If the maximum open position of the balls in the ball valves is a fixed position, then obviously the amount of back flow encountered before valve closure will vary substantially with the nature of the concrete and particularly the aggregate size in the concrete being pumped. This causes the surge and pressure fluctuation previously mentioned.
Also prior art pump manifolds are characteristically welded assemblies fabricated in substantial part from standard steel tubing and fittings. Accordingly, the ball valves typically are comprised of a cylindrical enclosure for the ball, bounded at one end by some form of annular inward extending valve seat, with means being provided for fixing the other limit of ball travel. The net result of such pump is that the manifold system provides rather substantial flow area discontinuities which tend to cause flow restriction and on ocassion outright jamming of the pump. Also, it will be noted that immediately adjacent the circumference of the ball there is a minimum concrete flow area, while at each side of the ball along the flow path there is a maximum flow area. Accordingly, the variation in flow area tends to cause jamming or packing as previously mentioned, and in addition, the regions of large flow area result in a greater than necessary volume of concrete in the manifold. While concrete itself is substantially incompressable, there may be substantial entrainment of air in the concrete, which of course is compressable, with the net result that surge may also be encountered because of the presence and/or variation in air in the mix, a factor dependent primarily upon the amount of water in the mix.
One prior art attempt to overcome some of these problems is described by Conklin, U.S. Pat. No. 2,734,667. Conklin utilizes a dual piston concrete pump wherein the valve equipped pistons comprised a ball which was disposed in a wire-like cage. On the downward stroke of the piston, the ball in cage closed the passageway between the feed stream and the outlet. On the upward stroke, the ball travelled until it came into contact with the bottom of the cage. A second ball valve was positioned beneath the ball valve in the cage. This second ball valve travelled between its valve seat and permanent radial pins disposed along the passageway. Another prior art concrete pump is disclosed by Delligatti, U.S. Pat. No. 3,140,801. Delligatti's pump also comprises a dual ball valve arrangement positioned along the passageway through which the concrete is pumped. In Delligatti's pump, each ball valve is retained between a valve seat and a permanent restricting means. In both the Conklin and the Delligatti concrete pumps, the problem or surging and of easily removable valves so as to provide for a method of cleaning the valves was not effectively solved as their pumps are complicated having a large number of components. Further, these prior art pumps suffer the previously discussed problem of not enabling the user the ability to change aggregate size without extensive modification to the pump. For example, Delligatti discussed the need for various piston chamber diameters.
In the present invention the problem of surging is effectively solved by adjusting the distance the ball may travel in the ball valves. In U.S. Pat. Nos. 2,734,677 and 3,140,801, while there was a disclosure of a pin being used to adjust the distance the ball in the ball valve was able to travel, this pin is not adjustable. Once the pin was in place, the distance of ball travel was permanently fixed. In the present invention, there is an easily modifiable means which provides a number of different settings which allows the balls to travel different distances in the ball valves, this providing a solution to the problem of surging in the concrete being pumped. Further, the present invention provides an assembly that is easily disassembled and cleaned.